Sen. Mike Duffy holds up his glass during the Maritime Energy Association's annual dinner in Halifax on Feb. 6, 2013. Duffy represents Prince Edward Island in the Senate but there is some controversy about his residency relating to housing allowances.Photo: Devaan Ingraham/The Canadian Press/Files

Nigel Wright, the chief of staff for Prime Minister Stephen Harper who wrote a personal $90,172 cheque to cover Conservative senator Mike Duffy’s improperly claimed living expenses, announced his resignation early Sunday morning.